63 
widely oscillating temperatures; the roots were of unequal length, 
but in the experiments made hitherto the rate of growth was found 
to be independent of the length, at least when the latter was between 
‘138 and 25 m.m. In experiments which last for more than 7 or 
less than 3'/, hours it is not impossible, that the initial length may 
have some effect on growth. 
The rate of growth was determined macroscopically at tempera- 
tures between 0° and 40° during 3'/, and 7 hours and the results 
have been represented by tables and curves. 
In table I successive columns indicate: 1. the number of seedlings 
in the experiment, 2. the temperature at which the experiment was 
carried out during 3'/, hours, 3. the growth in m.m. expressed as 
the mean, calculated in the usual manner. 
The same data, shown in table I for 3'/, hours, are shown in 
table II for observations of 7 hours’ duration. In addition the latter 
table has a fourth column, giving the calculated growth increment 
for 7 hours in the thermostat, if the rate of growth in the second 
period of 3'/, hours had been the same as in the first period of 
3'/, hours. 
The tables show that for experiments of 3'/, hours’ duration the 
optimum lies at 28°. Whilst at temperatures below 27° the rate of 
growth gradually diminishes, irregularities occur at higher tempera- 
tures; exterpolation according to BLACKMAN does not seem possible. 
Furthermore growth was observed at 0°; there is no sudden ces- 
sation of growth; Sacus’ representation of the minimum is therefore 
not correct. Probably something of this kind also applies to the 
maximum. 
Growth during 31/; hours in m.m. 
